Neil Patrick Harris's Twins Meet Oprah

"They're super healthy and they're happy," Harris says on Oprah's Next Chapter of the 19-month-old twins, who were born via surrogate in October 2010.

In Harris's and Burtka's telling, the twins' conception was a miracle of modern science, involving two embryos – one for each of them – and a surrogate. ("She was more like the oven," according to Burtka.)

The proud papas knew the surrogate but the egg donor was anonymous, though they were able to research her personal and medical history beforehand.

Harris tells Winfrey they "lucked out" that both of the embryos took.

And the twins are starting to develop distinct personalities. Gideon is "the shy one," according to Burtka, but both love the water and are taking swimming classes in preparation for the summer.

Oprah's Next Chapter with the Harris-Burtka family airs June 3rd at 9 ET on OWN.